The present invention relates to system and method for positionally locating a train/locomotive on a trackway system.
Various systems have been developed to track the movement of and/or location of railway locomotives on track systems including the system disclosed in U.S. Pat. No. 6,641,090 issued Nov. 4, 2003 to Thomas J. Meyer and in common assignment herewith in which inertial components (including accelerometers and gyroscopes) cooperate with GPS information to provide location data.
Track databases are maintained that store track information including the absolute and relative position of tracks and track transitions such as, for example, switches and turnouts. Ideally, railroad tracks are perfectly uniform and remain consistent with their original design as straight tangent sections connected by constant curve and spiral sections. In practice, however, weather and geographical conditions, train speeds, tonnage, and continued maintenance requirements contribute to railroad track non-uniformities. The Federal Track Safety Standards (FTSS) divide railroad track into nine (9) speed-related classifications as a function of speed with permissible variations of track geometry provided for each track class. Although the FRA (Federal Rail Administration) regulates the amount of track irregularities permitted for each track class (Class 1-7), most track database information carries errors that can change with time and which are often difficult to and expensive to ascertain with accuracy. Regardless of the issues related to the positional changes in the track consequent to time and usage, track surveys are rarely conducted with the accuracy required for positive train control.
As is often the case, disparities arise between the output of the train/locomotive mounted location determining system and the corresponding database information; at times, the disparities can be such that resolving these disparities sufficiently to resolve to a specific track with a high degree of confidence can be difficult.